Earth boring bit having air tube with removable cap

ABSTRACT

A drill bit has a plurality of air tubes extending into the bowl for separating entrained debris and liquids from air flow used to clean and cool bearings in the cutters of the bit. The air tube is assembled from a tube and a cap. The tube has open ends and a plurality of openings through the sidewall of the tube for allowing air to flow through the openings while preventing large debris from entering the tube. The lower end of the tube is inserted into an inner portion of a fluid passage, and the cap is secured to the upper end of the tube. The cap is removable for providing access to the interior of the tube when necessary to dislodge debris from within the tube.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to earth boring drill bits and specifically to an air tube for a bit that uses air flow as a cooling medium for the bearings.

[0003] 2. Description of the Prior Art

[0004] Earth boring bits of the rolling cutter type consist of three general types: (1) Those having sealed bearings that are lubricated with a liquid lubricant confined in the bearing area, (2) those having open bearings where the fluid in the well bore is free to enter the bearings, and (3) the air or gas cooled, unsealed bit that has unsealed bearings cooled by the flow of fluid through passages in the body and the bearing of each leg.

[0005] Inevitably, it seems, there are some liquid and particles of dust or other debris pumped through the drill pipe supporting the bit. Often there is particle contaminated water on the bottom of the hole that flows backwardly into the bit when the air supply is stopped. All too frequently these ingredients form obstructions in one or more of the passages leading to the bearings, block the flow of cooling fluid and cause excessive heating and failure of one of the bearings.

[0006] Since the so called “air bit” is often used to drill repeatedly shallow holes in the mining industry, the accumulation of detritus in the passages of the bit is manually removed by the workers. This task is difficult since access to the internal air passages is limited, and may involve the removal from inside the shank of the screening tubes used over the cooling passages. Then, water is flushed through the passages, and a rod used to dislodge the blockage. These cleaning efforts are time consuming and difficult, partly because access to the passages is restricted.

[0007] Air tubes extending into the bit have been used to limit the amount of debris entering the passages. Open- and closed-end tubes have been used, and these usually have slots or perforations along the side of the tubes. Open-end designs have the advantage of allowing access, but allow debris to enter the upper end of the air tube. Closed-end designs further limit debris entering the air tubes, but prevent ready access to the air passages.

SUMMARY OF THE INVENTION

[0008] A drill bit has a plurality of air tubes extending into the bowl for separating entrained debris and liquids from air flow used to clean and cool bearings in the cutters of the bit. The air tube is assembled from a tube and a cap. The tube has open ends and a plurality of openings through the sidewall of the tube for allowing air to flow through the openings while preventing large debris from entering the tube. The lower end of the tube is inserted into an inner portion of a fluid passage, and the cap is secured to the upper end of the tube. The cap is removable for providing access to the interior of the tube when necessary to dislodge debris from within the tube.

[0009] In a second embodiment, the cap has a skirt that extends downward to shield the openings in the tube. The skirt extends below the lowest opening and diverts liquids around the tube while allowing a sufficient flow of air to enter the openings.

[0010] In a third embodiment, the skirt is elongated to below the lowest opening, but provides for a narrow, flared entrance to the tube. Liquids tend to impinge on the flared surface, reducing the entrained liquid entering the openings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The novel features believed to be characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings.

[0012]FIG. 1 is a perspective view of an air tube assembly constructed in accordance with the present invention.

[0013]FIG. 2 is an enlarged, cross-sectional view of the upper portion of the air tube of FIG. 1.

[0014]FIG. 3 is a cross-sectional view of one leg of a drill bit with the air tube of FIG. 1 installed

[0015]FIG. 4 is a perspective view of an alternate embodiment of an air tube constructed in accordance with the present invention.

[0016]FIG. 5 is a perspective view of the upper portion of a second alternate embodiment of an air tube constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0017]FIG. 1 shows an air tube 11 constructed according to the present invention. Air tube 11 comprises tube 13 and cap 15, each of which maybe formed from various materials, though tube 13 is preferably formed from plastic and cap 15 is preferably formed from plastic or vinyl.

[0018] Cap 15 snaps onto the upper end of tube 13 and is removable to provide access to the interior of tube 13. Cap 15 comprises a flat, circular cover portion 17 and a cylindrical skirt section 19. Cover 17 is sized to be slightly larger than the upper end of tube 13, and skirt 19 depends from the outer perimeter of cover 17 for engaging the sidewall of tube 13. Cap 15 may have a slot 21, as shown, allowing cap 15 to be rotated with a bladed tool, such as a slot-head screwdriver, for removal of cap 13. Slot 21 extends through cover 17, and fluids can flow through slot 21.

[0019] Tube 13 is generally cylindrical, having open ends. Openings 23 are located toward the upper end of the sidewall of tube 13 and open into the interior of tube 13, openings 23 being shown as circumferential slots partially extending around the circumference of tube 13. Openings 23 are sized to prevent large debris or cuttings from passing through openings 23 and are spaced a small distance from each other in a vertical column. Toward the lower end of tube 13 is a barbed, or serrated, section 25 that engages a surface surrounding section 25 when tube 13 is installed in a drilling tool. Each rib of barbed section 25 is conical and deformable.

[0020]FIG. 2 is an enlarged cross-section of the upper portion of air tube 11, illustrating cap 15 mounted on tube 13. Detent 27, which maybe a circumferential ring or one of a series of separate bead portions, is located on the inner surface 29 of skirt 19. Detent 27 engages a recess 31 in outer surface 33 of tube 13, recess 31 also being one of a series of separate indentations or a circumferential ring. If cap 15 is formed from vinyl, detent 27 and recess 31 may be omitted due to the friction between cap 15 and tube 13.

[0021] Though not required, it is preferable that the upper end of tube 13 be defined by a plane that is not perpendicular to the central axis 35 of tube 13. The outer portion of tube 13 (being opposite openings 23 and to the left in the figure) has a larger height than the inner portion (containing openings 23 and to the right in the figure). The inner portion is closer to the axis of rotation of the bit than the outer portion. Likewise, cover 17 of cap 15 is parallel to the plane defining the upper end of tube 13, the inner portion of skirt 19 being shorter than the outer portion of skirt 19, skirt 19 being coaxial with tube 13. Detent 27 and recess 31 are located on a plane that is perpendicular to axis 35, so the inner portion of detent 27 is located closer to cover 17 than is the outer portion and the inner portion of recess 31 is located closer to the upper end of tube 13 than is the outer portion.

[0022] Because cover 17 lies in an inclined plane, the inner portion of skirt 19 is shorter that the outer portion of skirt 19. The pitch of the planes cause cap 15 to move axially upward relative to tube 13 when cap 15 is rotated relative to tube 13, such as by twisting cap 15 with a screwdriver engaging slot 21. As cap 15 is rotated on tube 13 from the installed position shown in the figures, the inner portion of the lower surface 36 of cover 15 rotates to the outer portion tube 13, camming cap 15 axially upward and away from tube 13 and disengaging detent 27 from recess 31. The full axial movement is achieved when cap 15 has been rotated 180° from the installed position.

[0023] Air tube 11 is shown in FIG. 3 after installation in a drilling bit 37. Bit 37 will typically have three cutter cones (not shown), each mounted on a bearing shaft 39 extending inward and downward from a leg 41 (only one shown). Lubrication passages 43, 45 extend through leg 41 and shaft 39, respectively, for carrying air or liquid lubricants to the bearing areas on the inner portion of shaft 39. The upper portion 47 of passage 43 is oversized to receive the lower end of tube 13 barbed section 25 of tube 13, the inner surface of upper section 47 being coarse or rough to enhance retention of tube 13, which is retained by a frictional fit. Tube 13 extends into a bowl area 49 in the interior of bit 37, bowl area 49 being in fluid communication with the interior of a drill string (not shown) used to turn bit 37. Openings 23 provide a flow path for fluid to pass into bowl area 49, then into air tube 11, and into passages 43, 45.

[0024] In operation, the lower section 25 of tube 13 is inserted into upper section 47 of a passage 43 in each leg 41, then cap 15 is installed on tube 13 to form air tube 11. Barbed section 25 deforms as tube 13 is pushed into upper section 47. Alternatively, air tube 11 may be assembled before installation into bit 37. Bit 37 is secured to the lower end of a drill string (not shown) and lowered into the well. Air is then pumped down the drill string and into bowl area 49 of bit 37. The air pressure causes the air to flow through openings 23 and into the interior of tube 11. The air then flows down into passage 43 and passage 45 to the bearing areas of bearing shaft 39 for clearing debris and cooling the cutters (not shown). If tube 13 or passages 43, 45 become blocked with debris, bit 37 can be removed from the drill string and cap 15 can be removed to provide access to clean the interior of tube 13 without the need to remove tube 13 from bit 37.

[0025]FIG. 4 shows an alternative embodiment of an air tube 51 in accordance with the present invention and used to separate liquids from the flowing air. Cap 53 has a cover 55 and a slot 57 for twisting cap 53 to remove cap 53 from tube 13. Like cover 17 of cap 15 (FIGS. 1 through 3), cover 55 is located in a plane that is parallel to the plane defining the upper end of tube 13, allowing cap 53 to be removed by rotating cap 53 relative to tube 13. Cap 53 has an elongated skirt 59 that extends to below the lowest opening 23 of tube 13 when cap 53 is installed on tube 13. Skirt 59 is U-shaped in cross-section, having sides 61 that extend inwardly as flat, planar sections, terminating at inner edges 63. When installed, inner edges 63 are closer to the axis of rotation of the bit than the opposite, outer side of cap 53. The open side defined by inner edges 63 aligns with openings 23 and shrouds, but does not block, openings 23. A plane across inner edges 63 may be tangent to or slightly inward of the inner portion of the sidewall of tube 13. Skirt 59 limits the direction from which fluid can flow into openings 23 and tends to further limit the amount of entrained debris that can enter tube 13. Because the drill bit is spinning, denser materials, such as water or lubricant within the air in the bit, are accelerated outwards and impinge on the inner wall of the bit. These materials then flow downward but do not enter tube 13.

[0026] A second alternate embodiment is shown in FIG. 5. Air tube 65 is formed by assembling tube 13 and cap 67 in the same manner as described above. Cap 67 comprises inclined cover 69, having slot 71, and skirt 73. Sides 75 extend inward, curving toward each other to form a narrowed throat area, then flaring outward and terminating at inner edges 77 to create a wider mouth. The open side between inner edges 77 aligns with and shrouds openings 23, and a plane across inner edges 77 maybe tangent to or slightly inward of the inner portion of the sidewall of tube 13. As fluid flows into the narrowed opening of skirt 73, water and other liquids may impinge on flared surface 79, reducing the amount of liquid that travels into openings 23 of tube 13.

[0027] The advantages of using the present invention include the ability to readily remove the end cap of the air tube, allowing access to the interior of tube. The tube and connected passage can then be cleaned of debris that passes through the openings in the air tube and lodges within the tube or passage. Also, the cap, being secured by a detent, is easily removed by rotating the cap relative to the tube. The cap can be formed to provide a water- or oil-separating function, limiting the amount of fluid entering the openings of the air tube.

[0028] While the invention has been shown in only some of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention. 

We claim:
 1. A drill bit, comprising: a body having at least one leg extending from the body, the body enclosing a bowl; a passage extending through the body and the leg, the passage being in fluid communication with the bowl; at least one tube extending from the passage and into the bowl, the tube having open upper and lower ends and being generally cylindrical, the tube having at least one opening along a sidewall of the tube, the lower end of the tube being inserted into the passage; and a cap on the upper end of the tube, the cap being removable to provide access to an interior of the tube.
 2. The drill bit of claim 1, wherein: the cap comprises a skirt depending from a cover of the cap, the skirt being in engagement with at least a portion of the sidewall of the tube.
 3. The drill bit of claim 1, further comprising: a cylindrical skirt depending from a cover of the cap, the skirt extending downward and terminating above the opening in the sidewall.
 4. The drill bit of claim 1, wherein: the opening in the sidewall is located on an inner side of the tube relative to an axis of the bit, an outer side of the tube being free of openings; and wherein the drill bit further comprises a skirt depending from a cover of the cap, the skirt extending downward and terminating below the opening, the skirt having two side portions that extend inwardly and terminate at spaced-apart inner edges, the side portions defining an open inner side that registers with the opening in the sidewall of the tube.
 5. The drill bit of claim 1, wherein: the opening in the sidewall is located on an inner side of the tube relative to an axis of the bit, an outer side of the tube being free of openings; and wherein the drill bit further comprises a skirt depending from a cover of the cap, the skirt extending downward and terminating below the opening, the skirt being generally U-shaped in transverse cross-section and having a curved outer portion and two parallel, straight side portions extending inwardly past the inner side of the tube, the straight side portions defining an open inner side that registers with the opening in the sidewall of the tube.
 6. The drill bit of claim 1, wherein: the opening in the sidewall is located on an inner side of the tube relative to an axis of the bit, an outer side of the tube being free of openings; and wherein the drill bit further comprises a skirt depending from a cover of the cap, the skirt extending downward and terminating below the opening, the skirt having a cylindrical outer portion and two concave inner portions that extend inwardly from the outer portion, the inner portions defining an open inner side that registers with the opening in the sidewall of the tube, the inner portions forming a throat area and a mouth, the throat area having a narrower width than the mouth.
 7. The drill bit of claim 1, wherein: the tube has a plurality of deformable ribs that frictionally engage the passage in the body.
 8. The drill bit of claim 1, wherein: a cover of the cap and the upper end of the tube are defined by planes which are at angles to a central axis of the tube, such that rotation of the cap relative to the tube causes the cap to move axially.
 9. The drill bit of claim 1, further comprising: a detent located on one of the cap and tube for engaging a recess located on the other of the cap and tube; and wherein a cover of the cap and the upper end of the tube are defined by planes which are at angles to a central axis of the tube, such that rotation of the cap relative to the tube causes the cap to move axially and disengage the detent from the recess.
 10. The drill bit of claim 1, further comprising: a slot located in a cover of the cap, the slot being sized for engaging a tool for rotating the cap relative to the tube.
 11. A drill bit, comprising: a body having at least one leg extending from the body, the body enclosing a bowl; a passage extending through the body and the leg, the passage being in fluid communication with the bowl; at least one tube extending from the passage and into the bowl, the tube having open upper and lower ends and being generally cylindrical, the lower end of the tube being inserted into the passage; a plurality of elongated openings along a sidewall of the tube, each opening extending partially around the circumference of the tube on an inner side of the tube, the openings being in an axial column; and a cap on the upper end of the tube, the cap having a skirt depending from a cover of the cap, the skirt being in engagement with at least a portion of the sidewall of the tube, the cap being removable to provide access to an interior of the tube.
 12. The drill bit of claim 11, wherein: the skirt extends downward and terminates below the opening, the skirt being generally U-shaped in transverse cross-section and having a curved outer portion and two parallel, straight side portions extending inwardly past the inner side of the tube, the straight side portions defining an open inner side that registers with the openings in the sidewall of the tube.
 13. The drill bit of claim 11, wherein: the skirt extends downward and terminates below the openings, the skirt having a cylindrical outer portion and two concave inner portions that extend inwardly from the outer portion, the inner portions defining an open inner side that registers with the openings in the sidewall of the tube, the inner portions forming a throat area and a mouth, the throat area having a narrower width than the mouth.
 14. The drill bit of claim 11, wherein: the tube has a plurality of deformable ribs that frictionally engage the passage in the body.
 15. The drill bit of claim 11, wherein: the cover of the cap and the upper end of the tube are defined by planes which are at angles to a central axis of the tube, such that rotation of the cap relative to the tube causes the cap to move axially.
 16. The drill bit of claim 11, further comprising: a detent located on one of the cap and tube for engaging a recess located on the other of the cap and tube; and wherein the cover of the cap and the upper end of the tube are defined by planes which are at angles to a central axis of the tube, such that rotation of the cap relative to the tube causes the cap to move axially and disengage the detent from the recess.
 17. The drill bit of claim 11, further comprising: a slot located in the cover of the cap, the slot being sized for engaging a tool for rotating the cap relative to the tube.
 18. A drill bit, comprising: a body having at least one leg extending from the body, the body enclosing a bowl; a passage extending through the body and the leg, the passage being in fluid communication with the bowl; at least one tube extending from the passage and into the bowl, the tube having open upper and lower ends and being generally cylindrical, the lower end of the tube being inserted into the passage; a plurality of elongated openings along a sidewall of the tube, each opening extending partially around the circumference of the tube on an inner side of the tube, the openings being in an axial column; and a cap on the upper end of the tube, the cap having a skirt depending from a cover of the cap, the skirt being in engagement with at least a portion of the sidewall of the tube, the cap being removable to provide access to an interior of the tube; and wherein the cover of the cap and the upper end of the tube are defined by planes which are at angles to a central axis of the tube, such that rotation of the cap relative to the tube causes the cap to move axially.
 19. The drill bit of claim 18, wherein: the skirt extends downward and terminates below the opening, the skirt being generally U-shaped in transverse cross-section and having a curved outer portion and two parallel, straight side portions extending inwardly past the inner side of the tube, the straight side portions defining an open inner side that registers with the openings in the sidewall of the tube.
 20. The drill bit of claim 18, wherein: the skirt extends downward and terminates below the openings, the skirt having a cylindrical outer portion and two concave inner portions that extend inwardly from the outer portion, the inner portions defining an open inner side that registers with the openings in the sidewall of the tube, the inner portions forming a throat area and a mouth, the throat area having a narrower width than the mouth.
 21. The drill bit of claim 18, wherein: the tube has a plurality of deformable ribs that frictionally engage the passage in the body.
 22. The drill bit of claim 18, further comprising: a detent located on one of the cap and tube for engaging a recess located on the other of the cap and tube; and wherein rotation of the cap relative to the tube disengages the detent from the recess.
 23. The drill bit of claim 18, further comprising: a slot located in the cover of the cap, the slot being sized for engaging a tool for rotating the cap relative to the tube.
 24. A drill bit, comprising: a body having at least one leg extending from the body, the body enclosing a bowl; a passage extending through the body and the leg, the passage being in fluid communication with the bowl; at least one tube extending from the passage and into the bowl, the tube having open upper and lower ends and being generally cylindrical, the lower end of the tube being inserted into the passage; an opening in the sidewall of the tube, the opening being located on an inner side of the tube relative to an axis of the bit, an outer side of the tube being free of openings; and a cap on the upper end of the tube, the cap being removable to provide access to an interior of the tube, the cap having a cover and a skirt; and wherein the skirt depends from the cover of the cap, the skirt extending downward and terminating below the opening, the skirt having two side portions that extend inwardly and terminate at spaced-apart inner edges, the side portions defining an open inner side that registers with the opening in the sidewall of the tube.
 25. The drill bit of claim 24, wherein: the side portions are flat, planar sections that are parallel to each other.
 26. The drill bit of claim 24, wherein: the side portions are concave sections that converge to form a throat and a mouth, the throat having a narrower width than the mouth.
 27. The drill bit of claim 24, wherein: the tube has a plurality of deformable ribs that frictionally engage the passage in the body.
 28. The drill bit of claim 24, wherein: the cover of the cap and the upper end of the tube are defined by planes which are at angles to a central axis of the tube, such that rotation of the cap relative to the tube causes the cap to move axially.
 29. The drill bit of claim 24, further comprising: a detent located on one of the cap and tube for engaging a recess located on the other of the cap and tube; and wherein the cover of the cap and the upper end of the tube are defined by planes which are at angles to a central axis of the tube, such that rotation of the cap relative to the tube causes the cap to move axially and disengage the detent from the recess.
 30. The drill bit of claim 24, further comprising: a slot located in the cover of the cap, the slot being sized for engaging a tool for rotating the cap relative to the tube. 